.\"	$OpenBSD: X509_ALGOR_dup.3,v 1.14 2019/06/06 01:06:59 schwarze Exp $
.\"	OpenSSL 4692340e Jun 7 15:49:08 2016 -0400
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.\" Copyright (c) 2016 Ingo Schwarze <schwarze@openbsd.org>
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.Dd $Mdocdate: June 6 2019 $
.Dt X509_ALGOR_DUP 3
.Os
.Sh NAME
.Nm X509_ALGOR_new ,
.Nm X509_ALGOR_free ,
.Nm X509_ALGOR_dup ,
.Nm X509_ALGOR_set0 ,
.Nm X509_ALGOR_get0 ,
.Nm X509_ALGOR_set_md ,
.Nm X509_ALGOR_cmp
.Nd create, change, and inspect algorithm identifiers
.Sh SYNOPSIS
.In openssl/x509.h
.Ft X509_ALGOR *
.Fn X509_ALGOR_new void
.Ft void
.Fn X509_ALGOR_free "X509_ALGOR *alg"
.Ft X509_ALGOR *
.Fo X509_ALGOR_dup
.Fa "X509_ALGOR *alg"
.Fc
.Ft int
.Fo X509_ALGOR_set0
.Fa "X509_ALGOR *alg"
.Fa "ASN1_OBJECT *aobj"
.Fa "int ptype"
.Fa "void *pval"
.Fc
.Ft void
.Fo X509_ALGOR_get0
.Fa "const ASN1_OBJECT **paobj"
.Fa "int *pptype"
.Fa "const void **ppval"
.Fa "const X509_ALGOR *alg"
.Fc
.Ft void
.Fo X509_ALGOR_set_md
.Fa "X509_ALGOR *alg"
.Fa "const EVP_MD *md"
.Fc
.Ft int
.Fo X509_ALGOR_cmp
.Fa "const X509_ALGOR *a"
.Fa "const X509_ALGOR *b"
.Fc
.Sh DESCRIPTION
.Fn X509_ALGOR_new
allocates and initializes an empty
.Vt X509_ALGOR
object, representing an ASN.1
.Vt AlgorithmIdentifier
structure defined in RFC 5280 section 4.1.1.2.
Such objects can specify a cryptographic algorithm together
with algorithm-specific parameters.
They are used by many other objects, for example certificates,
certificate revocation lists, and certificate requests.
.Pp
.Fn X509_ALGOR_free
frees
.Fa alg .
.Pp
.Fn X509_ALGOR_dup
copies
.Fa alg
by calling
.Xr i2d_X509_ALGOR 3
and
.Xr d2i_X509_ALGOR 3 .
.Pp
.Fn X509_ALGOR_set0
sets the algorithm OID of
.Fa alg
to
.Fa aobj
and the associated parameter type to
.Fa ptype
with value
.Fa pval .
If
.Fa ptype
is
.Dv V_ASN1_UNDEF
the parameter is omitted, otherwise
.Fa ptype
and
.Fa pval
have the same meaning as the
.Fa type
and
.Fa value
parameters to
.Xr ASN1_TYPE_set 3 .
All the supplied parameters are used internally so must
.Sy NOT
be freed after this call.
.Pp
.Fn X509_ALGOR_get0
is the inverse of
.Fn X509_ALGOR_set0 :
it returns the algorithm OID in
.Pf * Fa paobj
and the associated parameter in
.Pf * Fa pptype
and
.Pf * Fa ppval
from
.Fa alg .
.Pp
.Fn X509_ALGOR_set_md
sets
.Fa alg
to appropriate values for the message digest
.Fa md .
.Pp
.Fn X509_ALGOR_cmp
compares
.Fa a
and
.Fa b .
.Sh RETURN VALUES
.Fn X509_ALGOR_new
and
.Fn X509_ALGOR_dup
return a new
.Vt X509_ALGOR
object or
.Dv NULL
if an error occurs.
.Pp
.Fn X509_ALGOR_set0
returns 1 for success or 0 for failure.
.Pp
.Fn X509_ALGOR_cmp
returns 0 if
.Fa a
and
.Fa b
have identical encodings or non-zero otherwise.
.Sh SEE ALSO
.Xr ASN1_TYPE_set 3 ,
.Xr d2i_X509_ALGOR 3 ,
.Xr EVP_DigestInit 3 ,
.Xr X509_get0_signature 3 ,
.Xr X509_new 3 ,
.Xr X509_PUBKEY_get0_param 3
.Sh STANDARDS
RFC 5280: Internet X.509 Public Key Infrastructure Certificate and
Certificate Revocation List (CRL) Profile
.Sh HISTORY
.Fn X509_ALGOR_new
and
.Fn X509_ALGOR_free
appeared in SSLeay 0.4 or earlier and have been available since
.Ox 2.4 .
.Pp
.Fn X509_ALGOR_dup
first appeared in SSLeay 0.9.1 and has been avialable since
.Ox 2.6 .
.Pp
.Fn X509_ALGOR_set0
and
.Fn X509_ALGOR_get0
first appeared in OpenSSL 0.9.8h and have been available since
.Ox 4.5 .
.Pp
.Fn X509_ALGOR_cmp
first appeared in OpenSSL 0.9.8zd, 1.0.0p, and 1.0.1k
and has been available since
.Ox 4.9 .
.Pp
.Fn X509_ALGOR_set_md
first appeared in OpenSSL 1.0.1 and has been available since
.Ox 5.3 .
